Metric Screw Gauges | McMaster-Carr

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22 Products

Screw Size Identifiers

Metric

Find thread size, screw size, diameter, or drill bit size.

Metric
For Use With	For Thread Type	For Thread Location	For Thread Size	For Screw Size	For Drill Bit Size	Wd.	Ht.	Thick.		Each
Steel
Screws, Bolts, Threaded Rods	Metric	External	M8 × 0.75 mm, M8 × 1 mm, M8 × 1.25 mm, M9 × 0.75 mm, M9 × 1 mm, M9 × 1.25 mm, M10 × 0.75 mm, M10 × 1 mm, M10 × 1.25 mm, M10 × 1.5 mm, M11 × 0.75 mm, M11 × 1 mm, M11 × 1.5 mm, M12 × 1 mm, M12 × 1.25 mm, M12 × 1.5 mm, M12 × 1.75 mm, M14 × 1.25 mm, M14 × 1.5 mm, M14 × 2 mm	M8, M9, M10, M11, M12, M14	__	5 1/8"	5 3/8"	1/8"	000000000	000000
Screws, Bolts, Threaded Rods, Drill Bits	Metric	External	M2 × 0.25 mm, M2 × 0.4 mm, M2.2 × 0.25 mm, M2.2 × 0.45 mm, M2.5 × 0.35 mm, M2.5 × 0.45 mm, M3 × 0.35 mm, M3 × 0.5 mm, M3.5 × 0.35 mm, M3.5 × 0.6 mm, M4 × 0.5 mm, M4 × 0.7 mm, M4.5 × 0.5 mm, M4.5 × 0.75 mm, M5 × 0.5 mm, M5 × 0.8 mm, M5.5 × 0.5 mm, M6 × 0.75 mm, M6 × 1 mm, M7 × 0.75 mm, M7 × 1 mm	M2, M2.2, M2.5, M3, M3.5, M4, M4.5, M5, M5.5, M6, M7	7/32", 52 ga, 50 ga, 48 ga, 46 ga, 45 ga, 43 ga, 39 ga, 37 ga, 32 ga, 31 ga, 30 ga, 28 ga, 25 ga, 22 ga, 21 ga, 18 ga, 16 ga, 10 ga, 8 ga, 4 ga, B, D, J	3"	5 3/8"	3/32"	000000000	00000

Wall-Mount Thread-It Screw, Bolt, and Nut Size Identifiers

Mount to a wall for easy access, and thread your fastener into holes or onto plugs for quick and accurate size identification.

							Mounting Holes
For Use With	For Thread Type	For Thread Location	For Thread Size	Wd.	Ht.	Thick.	No. of	Hole Dia.	Fasteners Included		Each
Inch/Metric
Steel
Screws, Bolts, Threaded Rods, Nuts	UNC/UNF/Metric	External/Internal	6-32, 8-32, 10-24, 10-32, 1/4"-20, 1/4"-28, 5/16"-18, 5/16"-24, 3/8"-16, 3/8"-24, 7/16"-20, 1/2"-13, 1/2"-20, 9/16"-12, 9/16"-18, M4 × 0.7 mm, M5 × 0.8 mm, M6 × 1 mm, M7 × 1 mm, M8 × 1 mm, M8 × 1.25 mm, M10 × 1 mm, M10 × 1.25 mm, M10 × 1.5 mm, M12 × 1.25 mm, M12 × 1.5 mm, M12 × 1.75 mm, 7/16"-14	3"	39"	1/2"	3	5/16"	No	00000000	000000

Thread-It Screw, Bolt, and Nut Size Identifiers

Thread your fastener into holes or onto plugs for quick and accurate size identification.

Inch/Metric
For Use With	For Thread Type	For Thread Location	For Thread Size		Each
Steel
Screws, Bolts, Threaded Rods, Nuts	UNC/UNF/Metric	External/Internal	6-32, 8-32, 10-24, 10-32, 1/4"-20, 1/4"-28, 5/16"-18, 5/16"-24, 3/8"-16, 3/8"-24, 7/16"-14, 7/16"-20, 1/2"-13, 1/2"-20, M4 × 0.7 mm, M5 × 0.8 mm, M6 × 1 mm, M7 × 1 mm, M8 × 1 mm, M8 × 1.25 mm, M10 × 1 mm, M10 × 1.25 mm, M10 × 1.5 mm, M12 × 1.25 mm, M12 × 1.5 mm, M12 × 1.75 mm	00000000	000000
Metric
Steel
Screws, Bolts, Threaded Rods, Nuts	Metric	External/Internal	M3 × 0.5 mm, M4 × 0.7 mm, M5 × 0.8 mm, M6 × 1 mm, M7 × 1 mm, M8 × 1 mm, M8 × 1.25 mm, M10 × 1 mm, M10 × 1.25 mm, M10 × 1.5 mm, M12 × 1.25 mm, M12 × 1.5 mm, M12 × 1.75 mm, M14 × 1.5 mm, M14 × 2 mm, M16 × 1.5 mm, M16 × 2 mm, M20 × 1.5 mm, M20 × 2.5 mm, M24 × 2 mm, M24 × 3 mm	00000000	00000

Screw, Bolt, and Nut Size Identifiers

Inch/Metric

Metric

Use on external and internal fastener threads.

Inch/Metric
For Use With	For Thread Type	For Thread Location	For Screw Size	For Thread Pitch	For Nut Size	Wd.	Ht.	Thick.		Each
Plastic
Screws, Bolts, Threaded Rods, Nuts	__	External/Internal	No. 6, No. 8, No. 10, 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 3/4", 1", M6, M7, M8, M10, M12, M14, M16, M18, M20, M22	__	No. 8, No. 10, 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8"	9"	3 3/4"	1/64"	000000000	000000
Metric
Plastic
Screws, Bolts, Threaded Rods, Nuts	Metric	External/Internal	M6, M7, M8, M10, M12, M14, M16	1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm	M10, M11, M13, M17, M19, M22, M24	5 1/4"	3 3/16"	1/64"	000000000	0000

Threads per Inch and Thread Pitch Identifiers

Determine threads per inch and thread pitch on nuts, bolts, and other fasteners. Identifiers in a variety of sizes are riveted together in a fan design—pull one out and hold it against your threads to see if it fits. Once you’ve found a match, fold identifiers in to store them in your pocket or tool bag.

						Folded
For Use With	For Thread Type	For Thread Location	For Threads per Inch	For Thread Pitch	No. of Identifiers	Lg.	Wd.	Manufacturer	Manufacturer Model No.		Each
Inch/Metric
Steel
Screws, Bolts, Threaded Rods, Nuts	UNC/UNF/Metric	External/Internal	4, 4 1/2, 5, 5 1/2, 6, 7, 8, 9, 10, 11, 11 1/2, 12, 13, 14, 15, 16, 18, 20, 22, 24, 26, 28, 29, 30, 32, 34, 36, 38, 40, 42	0.4 mm, 0.5 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.9 mm, 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm	51	2 3/4"	1/2"	__	__	0000000	000000
Screws, Bolts, Threaded Rods, Nuts	UNC/UNF/Metric	External/Internal	4, 6, 8, 10, 11, 11 1/2, 12, 13, 16, 20, 28, 32, 40, 56	0.5 mm, 0.75 mm, 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 6 mm	28	2 3/4"	1/2"	__	__	0000000	00000
Screws, Bolts, Threaded Rods, Nuts	BSW/Metric	External/Internal	4, 4 1/2, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 18, 19, 20, 22, 24, 25, 26, 28, 30, 32, 36, 40, 48, 60, 62	0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.9 mm, 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm	52	2 3/4"	1/2"	__	__	00000000	00000
Screws, Bolts, Threaded Rods, Nuts	BSW/Metric	External/Internal	4, 4 1/2, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 18, 19, 20, 22, 24, 25, 26, 28, 30, 32, 36, 40, 48, 60, 62	0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.9 mm, 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm	50	2 3/4"	1/2"	__	__	00000000	00000
Metric
Steel
Screws, Bolts, Threaded Rods, Nuts	Metric	External/Internal	__	0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.75 mm, 1.8 mm, 1.9 mm, 2 mm, 2.5 mm	28	2 1/2"	1/2"	Starrett	156M	0000000	00000
Screws, Bolts, Threaded Rods, Nuts	Metric	External/Internal	__	0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.75 mm, 1.8 mm, 1.9 mm, 2 mm, 2.5 mm	28	2 3/4"	1/2"	__	__	0000000	00000
Screws, Bolts, Threaded Rods, Nuts	Metric	External/Internal	__	0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.9 mm, 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm	22	2 3/4"	1/2"	__	__	0000000	00000
Screws, Bolts, Threaded Rods, Nuts	Metric	External/Internal	__	0.5 mm, 0.75 mm, 1 mm, 1.1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm, 11.5 mm	27	3 1/2"	5/8"	Starrett	159M	00000000	00000
Stainless Steel
Screws, Bolts, Threaded Rods, Nuts	Metric Trapezoidal	External/Internal	__	2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 12 mm, 16 mm, 20 mm	12	4 3/4"	3/4"	__	__	00000000	00000

Thread Identifier Sets

Set includes calipers and gauges to identify external and internal threads.

			Container
For Use With	For Thread Type	For Thread Location	Type	Material	Includes		Each
Inch, Metric
Steel
Screws, Bolts, Threaded Rods, Nuts, Pipe	NPT, UNC, UNF, BSPT, BSPP, Metric	External/Internal	Folding Case	Plastic	Caliper, Instruction Book, Two Steel Angle Gauges, Two Steel Gauges	000000	000000

Pipe Thread and Thread Pitch Identifiers

In addition to checking NPT and BSPT pipe sizes, use the two included gauges for measuring thread pitch.

For Thread Type	For Pipe Size	For Gender	Wd.	Ht.	Thick.	Thread Size Identifier Material	Thread Pitch Identifier Material	Color		Each
BSPT, NPT	1/8, 1/4, 3/8, 1/2, 3/4, 1, 1 1/4, 1 1/2, 2	Female, Male	9"	4 1/4"	1/4"	Plastic	Steel	Blue	000000	00000

Diameter Identifiers

Measure the outside diameter of small round- and hex-shaped objects such as rods, drill bits, bolts, and tubing with this pocket-size tool. This identifier has wear-resistant etched markings.

Diameter Measuring Range					Graduation
Inch	Metric, mm	Overall Lg.	Graduation Marks	Color	Mark Style	Color	Belt Clip		Each
Inch/Metric
Aluminum
3/32"-1 1/8"	4-26	5 1/2"	64ths, Millimeters	Blue	Etched	White	With Belt Clip	000000	000000

Grease Fitting Size Identifiers

Take the guesswork out of determining the thread type and size of a grease fitting. Screw the shank of a grease fitting into the labeled holes of these identifiers until you find the one that fits.

Inch, Metric
For Thread Type	For Thread Location	For Thread Size	For Screw Size	For Pipe Size	Wd.	Ht.	Thick.		Each
Aluminum
NPT, SAE-LT, BSW, UNF, BSPT, BSF, Metric	External	3/16"-32, 1/4"-20, 1/4"-26, 1/4"-28, 5/16"-18, 5/16"-22, 5/16"-24, 3/8"-20, 3/8"-24, 1/2"-12, M6 × 0.75 mm, M6 × 1 mm, M8 × 1 mm, M8 × 1.25 mm, M10 × 1 mm, M10 × 1.5 mm	1/8", 1/4"	1/8, 1/4, 3/8	8 1/2"	3"	1/4"	0000000	000000

Threads per Inch and Thread Pitch Size Checkers

Inspect fasteners and verify threads with this checker. It includes three wires for each of the pitch diameters. Select the wire that best fits the threads; then calculate the pitch diameter with the equations provided.

							Wire
For Use With	For Thread Type	For Thread Location	For Threads per Inch	For Thread Pitch	For Acme Threads per Inch	No. of Wires	Lg.	Material	Container	Container Material		Each
Inch; Metric
Screws, Bolts, Threaded Rods, Pipe	NPT, UNC, UNF, Metric, Acme	External	3, 3 1/2, 4, 4 1/2, 5, 5 1/2, 6, 7, 7 1/2, 8, 9, 10, 11, 11 1/2, 12, 13, 14, 16, 18, 20, 24, 27, 28, 32, 36, 40, 44, 48	0.5 mm, 0.6 mm, 0.7 mm, 0.75 mm, 0.8 mm, 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm	3, 4, 5, 6, 8, 10, 12, 14, 16	48	2 3/4"	Stainless Steel	Pouch	Vinyl	000000	000000

Thread Gauges for Lug Nuts

Identify the most common bolt thread sizes.

For Thread Size	For Thread Location	Material		Each
7/16"-20 1/2"-20 9/16"-18 M12 × 1.25 mm M12 × 1.5 mm M12 × 1.75 mm M14 × 1.25 mm M14 × 1.5 mm M14 × 2 mm M16 × 1.5 mm	External, Internal	Aluminum	00000000	000000